ClassCastException类扩展android.location.Location

Question

这是另一个我搞不懂的bug。

我有一个类ExtendedLocation extends Location，它在被currentGpsLocation = new ExtendedLocation((ExtendedLocation) location);实例化时抛出ClassCastException

查看堆栈跟踪绝对不会告诉我任何可能的解决方案。也许比我聪明的人能加入进来。

我在java/android方面很新，所以对一些人来说，这可能是一个简单的问题，只是对我来说不是。

异常

: java.lang.ClassCastException: android.location.Location
:   at ru.alperez.gpsdub.GpsActivity$1.onLocationChanged(GpsActivity.java:485)
:   at android.location.LocationManager$ListenerTransport._handleMessage(LocationManager.java:227)
:   at android.location.LocationManager$ListenerTransport.access$000(LocationManager.java:160)
:   at android.location.LocationManager$ListenerTransport$1.handleMessage(LocationManager.java:176)
:   at android.os.Handler.dispatchMessage(Handler.java:99)
:   at android.os.Looper.loop(Looper.java:130)
:   at android.app.ActivityThread.main(ActivityThread.java:3687)
:   at java.lang.reflect.Method.invokeNative(Native Method)
:   at java.lang.reflect.Method.invoke(Method.java:507)
:   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
:   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
:   at dalvik.system.NativeStart.main(Native Method)

ExtendedLocation.class

package ru.alperez.model;

import org.json.JSONException;
import org.json.JSONObject;

import android.location.Location;

public class ExtendedLocation extends Location{

    public ExtendedLocation(ExtendedLocation l) {
        super(l);
    }

    public ExtendedLocation(String provider) {
        super(provider);
    }

    public JSONObject toJSON() throws JSONException {
        JSONObject ret = new JSONObject();
        ret.put("accuracy", this.getAccuracy());
        ret.put("altitude", this.getAltitude());
        ret.put("bearing", this.getBearing());
        ret.put("lat", this.getLatitude());
        ret.put("lon", this.getLongitude());
        ret.put("provider", this.getProvider());
        ret.put("speed", this.getSpeed());
        ret.put("time", this.getTime());
        return ret;
    }

    public static ExtendedLocation fromJSON(JSONObject jLocation) {
        ExtendedLocation ret = null;
        try {
            ret = new ExtendedLocation(jLocation.optString("provider"));
            ret.setAccuracy((float) jLocation.optDouble("accuracy"));
            ret.setAltitude(jLocation.optDouble("altitude"));
            ret.setBearing((float) jLocation.optDouble("bearing"));
            ret.setLatitude(jLocation.optDouble("lat"));
            ret.setLongitude(jLocation.optDouble("lon"));
            ret.setSpeed((float) jLocation.optDouble("speed"));
            ret.setTime(jLocation.optLong("time"));
        } catch (Exception e) {
            ret = null;
        }
        return ret;
    }
}

违规代码

    @Override
    public void onLocationChanged(Location location) {
        Log.d(TAG, "LocationListener::onLocationChanged: "+location);
        try
        {
            currentGpsLocation = new ExtendedLocation((ExtendedLocation) location);
            Log.d(TAG, "LocationListener::onLocationChanged:currentGpsLocation "+currentGpsLocation);
        }
        catch (ClassCastException e)
        {
            Log.d(TAG,"ExtendedLocation failed.",e);
            return;
        }
        if (!USE_NMEA) {
            populateCurrentGpsData(currentGpsLocation, lastFixState, referenceGpsPoint);
        }
    }

Answer 1

onLocationChanged由LocationManager调用。对象由管理器传递，它不是类的对象。这里没有像您这样的构造函数：

public ExtendedLocation(ExtendedLocation l) {
    super(l);
}

试着将其替换为：

public ExtendedLocation(Location l) {
    super(l);
}

这条线来自onLocationChanged

  currentGpsLocation = new ExtendedLocation((ExtendedLocation) location);

变成：

  currentGpsLocation = new ExtendedLocation(location);

Answer 2

将ExtendedLocation构造函数的参数更改为Location，并从调用以下内容中删除类转换：currentGpsLocation = new ExtendedLocation(location);

Answer 3

您正在尝试将Location转换为ExtendedLocation

currentGpsLocation = new ExtendedLocation((ExtendedLocation) location);
                                          ^^^^^^^^^^^ here ^^^^^^^^^^

这是不允许的。ExtendedLocation是Location。相反，情况并非如此：Location不是ExtendedLocation。因此，不能将Location传递给ExtendedLocation。

不过，你不需要这个。你必须改变两个点：

将上述行更改为

currentGpsLocation = new ExtendedLocation(location);

并将类ExtendedLocation的构造函数更改为接受Location而不是ExtendedLocation

public ExtendedLocation(Location l) {
    super(l);
}